OXIDATION PROFILES OF THERMALLY AGED NITRILE RUBBER

The thermal degradation of a commercial, stabilized, unfilled nitrile (Buna-N) rubber material was investigated at temperatures in the range 85-140 degrees C. The resulting heterogeneous oxidation, due to diffu sion limitations in oxygen availability, was studied using infrared mi croscopy and modulus profiling. Degradation-related spectral changes w ere observed primarily in the hydroxyl, carbonyl and ester regions; qu antitative analysis revealed identical oxidation profiles for these ch romophores. These chemical oxidation profiles (carbonyl formation) wer e correlated with mechanical modulus (hardness) profiles. Degradation of the sample proceeds via a linear increase in the carbonyl concentra tion, but an exponential increase in the modulus with time. It is conc luded that the profile development and aging behavior can be described by a diffusion-limited autoxidation mechanism which can be modeled co mputationally. The results are compared to those of a previously studi ed carbon-black-filled material. Published by Elsevier Science Limited .